Report

FZJ-2016-05733

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Berechnung des lokalen Wärmeübergangs im Einlaufbereich von Rohren veränderlichen Querschnitts unter Berücksichtigung variabler Stoffwerte

Rechenauer, C.FZJ* ; Achenbach, E.FZJ*

1990
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/12646

Report No.: Juel-2384

Abstract: Hot gas is fed into a heat exchanger and is cooled down there. High local heat transfer coefficients arise in the inlet region of the water-cooled nozzle due to the entrance effect in the boundary layer which may result in the wall becoming locally overheated. In order to specify the most,favourable form possible for the inlet, the local heat transfer is calculated for cylindrical pipe geometries with a rounded inlet andfor conical pipe geometries similarly with a rounded inlet. To this end, the velocity field of the flow is first determined with the aid of the potential theory. The resulting velocity distribution along the inlet contour is used, via a boundary laver calculation, to determine the velocity and temperature profile and thus also the local Nusselt number along the contour. Studies are made both of laminar and also of the subsequent turbulent,fow, including the transition point. The properties mqy be regarded as variable. The differential equation system is solved by a numerical finite-difference method after implementation of the Mangier and the Blasius transformations. The theoretical results are in good agreement with own experimental results. The maximum Nusselt numbers are determinedfor the cylindrical pipe inlet at the transition point 'laminar-turbulent' which is observed near the transition from the inlet curvature into the pipe. Even for large curvature radii they are clearly above the maximum values occurring for the conical pipe inlet. For the latter geometry the critical position is at the transition from the cone to the cylindrical pipe. The thermal stresses on the tube material are thus lower for the conical pipe inlet than for the cylindrical geometry.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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